1. Mechanisms involved in mineral oil plasmacytomagenesis in the BALB/c mouse is the principal problem of the laboratory. Plasmacytomagenesis appears to be a 2-staged process. Stage 1 involves the formation of transformed cells, stage 2 involves the selective proliferation of these cells. Specific genes determine susceptibility to transformation. The oil granuloma provides an essential microenvironment for early growth of plasmacytoma cells. From crosses of the plasmacytomagenesis resistant DBA/2 and susceptible BALB/c multiple congenic strains are being developed to identify resistance genes. Studies continue to determine the role of type C viruses in initiating plasma cell transformation. Microenvironmental growth dependency is being studied, in millipore diffusion chambers where the role of specific cells and factors can be determined. 2. Immunochemical studies of myeloma proteins continue to determine 1) the number of V-kappa isotype groups in the mouse; 2) to build spacefilling hypothetical models of antigen binding myeloma proteins; 3) to determine the structural basis of idiotypes; 4) new antigen binding properties. 3. New allelic V-regions genetic markers are being characterized.